In modern network communications, a source may wish to multicast the same content to multiple destinations simultaneously. A basic way of accomplishing this is to concurrently transport the content over a plurality of individual point-to-point (P2P) label-switched-paths (LSPs) between the source and respective destinations. In some instances, one or more of the P2P LSPs may extend from an ingress edge router of an intermediate domain to an egress edge router of the same or different intermediate domain, where the ingress edge router connects to the source and the egress edge router connects to a respective destination. Because managing multiple P2P LSPs may be cumbersome and inefficient, one or more of the P2P LSPs (or portions thereof) may be aggregated into a point-to-multi-point (P2MP) LSP, which may resemble a tree whose trunk is rooted at a source (or an ingress edge router connecting to the source) and whose branches extend to egress edge routers (e.g., the leaves) connecting to the respective destinations.
Computation of a P2MP LSP that extends through only one autonomous system (AS), e.g., local routing domain controlled by unique routing policy, may be performed centrally by a single Path Computation Entity (PCE) that has access to the AS domain topology information. However, central computation of a P2MP LSP extending through multiple AS domains (e.g., an inter-domain P2MP LSP) may be difficult or impossible because there may not exist a central database containing the topology information of each relevant AS domain. For instance, servers in the provider domain may not contain information relating to the source and/or destinations (e.g., topology information of the source/destination domains). Specifically, many AS domains do not disseminate their local topological information to external entities (e.g., non-native PCEs or nodes in other AS domains) for privacy and/or security reasons. Even when the involved AS domains are willing to disseminate their topological information, central computation may be impractical because storing and/or updating the topological information for a large number of AS domains may be quite burdensome. As such, computation of P2MP or P2P LSPs requiring information (e.g., topology information) that relates to other domain (e.g., LSPs crossing into other domains or terminating at egress routers that forward the content to external domains/destinations) may be performed in a distributed manner using a plurality of PCEs that are locally positioned in or near the various AS domains (e.g., a source PCE, a provider PCE, a destination PCE, etc.). PCE-based architectures are discussed in detail in Internet Engineering Task Force (IETF) publication Request for Comments (RFC) 4655, and set up of a P2MP LSP is discussed in IETF publication RFC 4875, both of which are incorporated herein by reference as if reproduced in their entireties.